Wood Moisture Content Research Articles

Effect of Samples Length on the Characteristics of Moisture Transfer and Shrinkage of Eucalyptus urophylla Wood during Conventional Drying

Moisture transfer influences wood deformation and moisture content (MC) distribution during conventional drying of Eucalyptus urophylla wood. This study aims to investigate the effect of sample length (30, 100, and 200 mm) on moisture distribution and transfer in different directions and locations and on deformation of wood. The results showed that when the MC was above the fiber saturated point (FSP), the drying rate decreases exponentially with an increase of sample length; however, below the FSP, there was no obvious relationship between the drying rate and sample length and above the FSP, the moisture distribution was non-uniform along tangential, radial, and longitudinal directions and became even below the FSP, which was more significant in the middle location of wood. The greatest MC differences occurred between the surface and sub-central layers along the tangential and radial direction, which were between the end and sub-middle locations along the longitudinal direction. The effect of sample length on the MC distribution and MC differences along wood in the three directions depended on locations and the MC stage of wood; most of the free water and bound water transferred from the wood central to the ends along the longitudinal direction for three sets of samples. Bound water diffusion significantly slowed as the sample length exceeded 200 mm; sample length affects wood collapse and its recovery, but the drying rate has a lesser effect on collapse for samples with a length below 200 mm.

Analysis of surface roughness of chemically impregnated Scots pine processed using frame-sawing machine

ABSTRACT The objective of this work was to evaluate the effect of the impregnation process of pine wood (Pinus sylvestris L.) on roughness parameters of the surface processed on a frame sawing. The samples were dried and impregnated using a commercial procedure by a local company. The touch method with the use of measuring stylus (pin) was employed to determine of surface roughness of the samples considering parameters, namely, arithmetical mean roughness value (Ra), total height of the roughness profile (Rt), maximum height of roughness profile (Rz) and root-mean-square roughness (Rq). All measured values of the analysed surface roughness parameters were normalised by the raw density of wood in order to eliminate the effect of differences in wood density and moisture content of the tested samples of impregnated and non-impregnated pine. Generally, no effect of feed per tooth was observed for the analysed values of f z1 = 0.11 mm and f z2 = 0.22 mm on the surface roughness parameters. Only for the parameter Rq of impregnated wood was a significant effect of feed per tooth observed. The effect of the pine wood impregnation process on all analysed surface roughness parameters was observed for both analysed feeds per tooth.

The Influence of Processing Conditions on the Quality of Bent Solid Wood from European Oak

Bending of solid wood from European oak is one of the most demanding technological processes due to its specific structural and physical properties and variability. We investigated the influence of wood moisture content (MC) and stiffness, determined by NDT, as well as previous drying methods on the bending ability of the wood. The best quality was obtained with bending specimens bent at a moisture content of at least 16% and quarter- or semi-quartersawn. The number of rejected specimens increased slightly when HF bending was used. Single-stage predrying of oak to a final MC of 8% resulted in a high rejection rate (>70%) regardless of drying technique. The acceptance rate was higher for less stiff specimens where the ratio of ultrasonic velocity in the straight (vS) and bent region (vB) was less than 0.5 (vB/vS).

Laboratory Durability Testing of Preservative-Treated Wood Products

Recently, certain European standards have allowed for the classification of the biological durability of chemically modified wood and preservative-treated wood, including treated products, but necessary methods for representative sampling and testing are lacking. Instead of sampling from products that can contain areas of varying durability, this study aimed at testing full-size products. Sections of untreated and preservative-treated terrace decking and palisades were incubated with pure cultures of brown and white rot fungi. Instead of mass loss, the decayed cross-sectional area was determined. The spatial distribution of decay and wood moisture content was investigated. After 16 weeks of incubation, all untreated product specimens showed signs of decay independent of the test fungus. The treated specimens were less affected. The mean and the maximum decayed cross-sectional areas were well correlated, for both the total and the sapwood cross-sections. The wood moisture content after incubation was always favorable for fungal decay, but highest where the specimens were in direct contact with the malt agar. Different infestation pathways became evident: (1) from the sapwood mantle, (2) via radial checks, and (3) from the end-grain. The latter should be prevented in order to better mimic real outdoor exposure conditions.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ СОРБЦИОННОЙ ВЛАЖНОСТИ ДРЕВЕСИНЫ И ФАНЕРЫ, ИЗГОТОВЛЕННОЙ НА ЕЁ ОСНОВЕ

The article presents a comparative analysis of the results of determining the sorption moisture content of deciduous and coniferous wood and plywood made from these types of wood. It was found that the sorption humidity of pine wood is lower than softwood plywood by 0.7-9 %, and the sorption humidity of birch wood, on the contrary, is higher than plywood based on it by 7.4-15.13 %, depending on the relative humidity of the air

Moisture performance of various wooden shingles designs tested on the Golobar cable yarding

ABSTRACT Wood is a traditional roofing material in Europe and other parts of the world. In the seventeenth century, wooden roofing was generally used on more important buildings, but today it is mainly used on huts and houses in the Alpine regions. As wooden roofing is expensive, we investigated the possibility of extending the service life of the roofing through material selection and details. The roof of the Golobar cable yarding was covered with shingles made of spruce (Picea abies) and larch (Larix decidua). Part of the spruce roofing was thermally modified and/or treated with a water-wax emulsion. On the underside, we cut grooves in selected roof shingles to increase the specific surface of the wood and to accelerate drying after rainfall. In addition, wood moisture monitoring sensors were installed on the roof shingles. Based on three years of the wood moisture content measurements, it can be concluded that among shingles made of untreated spruce wood, the highest moisture content was recorded for shingles with a rectangular cross-section without additional grooves. The additional grooves positively affected the moisture performance of wood. Treating the wood with Silvacera wax had an even more pronounced effect on the moisture content of the shingles than the grooves.

Effect of Seawater with Average Salinity on the Moisture Content, Ash Content and Tensile Strength of Some Coniferous Wood.

In this paper, the differences in mechanical strength tested during the static tensile and compression test of Scots pine (Pinus sylvestris L.), European larch (Larix decidua) and Norway spruce (Picea abies) wood exposed to continuous soaking in water with a salinity of 7‱ were determined. The value of salinity corresponded to the average salinity on the Polish Baltic coast. This paper also aimed to examine the content of mineral compounds absorbed during four cycles of two weeks each. The essence of the statistical research was to identify the effect of the mineral range compounds and salts depending on the mechanical strength of the wood. Based on the results of the experiments, it can be concluded that the medium used has a specific effect on the wood species' structure. The effects of soaking on the wood parameters depend obviously on the type of wood. A tensile strength test of pine, as well as the tensile strength other species, was enhanced by incubating it in seawater. A native sample's initial mean tensile strength was 82.5 MPa, which increased to 94.8 MPa in the last cycle. It was found that the larch wood had the lowest tensile strength difference (9 MPa) of the woods studied in the current study. Four to six weeks of soaking was necessary to notice an increase in tensile strength.

Technology and properties of modified wood for low-rise construction

Subject of research: the article considers a relatively new material for low-rise construction modified wood solid wood with directionally altered physical properties, the natural properties of which are improved as a result of the use of modern woodworking technologies.
 Purpose of research: to consider the technology of obtaining modified wood for low-rise construction with increased operational properties.
 Methods and objects of research: hardwood birch, wood from hard-to-feed conifers pine; the proposed technology for producing modified wood allows you to obtain a new material with indicators corresponding to hardwood, due to through impregnation of the log with a modifier an aqueous solution of carbamide.
 Main results of research: the technology of obtaining modified wood increases its operational properties, when drying modified wood, the moisture content of wood decreases to 8 %, the content of carbamide in wood after impregnation is up to 8-10 %, density 700-730kg/ m3, strength 100-123MPa, during the pressing process, the height of the bars of modified wood decreases to 40 %, while the transverse dimensions of the bars of modified wood remain the original.

Effects of Temperature during Oil Heat Treatment on the Quality Improvement of Mindi (Melia azedarach) and Sengon (Falcataria moluccana) Woods

Fast growing wood has high potential in increasing numbers but has a low quality so that it requires modification to improve wood quality. Oil heat treatment (OHT) is one of a wood modification method using vegetable oil as a heat conducting medim. The objective of this study was to analyze the effect of temperature OHT on color change (ΔL*, Δa*, Δb*, and ΔE), physical properties (density, moisture content, water absorption, and weight changes), and the compressive strength of mindi (Melia adezarach) and sengon (Paraserianthes falcataria). OHT was conducted using 2 hours duration on temperature 180C, 200C, 220C, and 240C. The results showed that the effect of temperature on wood color inflicted an increase in the values of ΔL*, Δa*,Δb*, and ΔE on higher temperature of OHT. The effect of temperature on the physical properties of wood results in an increase on density at certain temperature and wood species as well as decreasing moisture content, water absorption, and weight changes of wood on higher temperature of OHT. The effect of temperature on mechanical properties of wood results in increasing compressive strength at certain temperatures and types of wood, but there is decrease compressive strength in the higher temperature of OHT.Keywords: Color change, oil hot treatment, mechanical properties, physical properties

Efficacy of Biological and Chemical Control Agents against Heterobasidion Spore Infections of Norway Spruce and Scots Pine Stumps on Drained Peatland

Treatment of conifer stumps with a control agent effectively prevents Heterobasidion spore infections in summer cuttings and protects the residual stand and the next tree generation from damage caused by Heterobasidion root rot. Thus far, stump treatment experiments have been carried out in mineral soils, and no information is available on the efficacy of stump treatment agents in boreal peatland conditions. In the present study, biological and chemical control agents (Phlebiopsis gigantea and urea, respectively) were tested in Scots pine and Norway spruce stands subjected to thinning, cap cutting, and clearcutting on drained peatland in Central Finland. The control efficacy of urea was high in both spruce and pine stumps (on average 99.5 and 85.3%, respectively), while the efficacy of P. gigantea was highly variable on both tree species and ranged from full protection down to negative control effect, i.e., there were more Heterobasidion infections on the treated than untreated half of the stumps. The moisture content of the stump wood or the thickness of the peat layer did not affect the control efficacy of either control agent. These results emphasize a need for further studies to determine the reasons for the unsteadiness of the biological control in peatland conditions.

The flame spread performance over discrete wooden chips varying wood species

Wood is believed to be a good material used for the thermal insulation of building. However, the wood species vary greatly from region to region in China. With an aim to have a deep understanding of the influence of wood species on upward flame spread performance, a series of tests were conducted to obtain the profile of mass loss rate (MLR), flame spread rate (FSR), total burning duration (TBD), and the maximum flame characteristic length (MFL) by using a traditional flame spreading measurement facility. During the tests, beech wood, fir wood, pine wood, camphor wood and elm wood were selected as typical samples. The results and discussion indicate that wood species imposed a strong effect on the flame spread performance. The total burning duration (TBD) of wood with high moisture content and high solidity is significantly higher than that of other types of wood. Softwoods with higher lignin content and lower hemicellulose can increase the FSR to a certain extent. Moreover, the moisture content of wood is found to have a big impact on the MLR. Based on the discussion of different parameters, it can be judged that the fire safety of the historic wooden buildings made of Fir wood is more excellent than others.

Digital Twin for Monitoring In-Service Performance of Post-Tensioned Self-Centering Cross-Laminated Timber Shear Walls

A digital twin (DT) can be defined as a multiphysics, multiscale model in which a digital model, such as a building information model (BIM), is updated based on data obtained from a physical system, such as sensor data, results from probabilistic simulations, and material/structural models. This study describes sensor data integration within a BIM as the first critical step toward the implementation of DTs to support structural health monitoring (SHM). In particular, the study defines a methodological approach used to integrate the as-built geometry of existing buildings, as well as their material properties and sensor data into a digital model to assist in accessing sensor data to assess a building’s structural performance. A mass-timber structural system consisting of post-tensioned cross-laminated timber (CLT) self-centering shear walls at the George W. Peavy Forest Science Center (“Peavy Hall”) at Oregon State University was used as a case study to test the proposed approach. The BIM of the shear walls was developed using a Scan-to-BIM approach by converting light detection and ranging point clouds into a BIM. Sensors in the building recorded environmental and structural parameters influencing the long-term performance of the shear walls. Measurands included relative humidity, air and wood temperature, wood moisture content, displacements, and deformations of shear walls. The precise placement of these sensors and the possibility to associate the measured parameters of these entities within a BIM is hypothesized to assist with data management by adding a spatial element to data and analysis results. In addition, the integration into the IFC-BIM platform of a material- and phenomena-specific warning tool allows to promptly identify areas of concern in the monitored building. This can support facility managers in planning inspection and maintenance activities and eventually could lead to the prolonged service life of a building.

Optimization of wood machining parameters using artificial neural network in CNC router

This study aims to determine the optimal CNC (Computer Numerical Control) machining conditions using an artificial neural network. For this purpose, Fagus orientalis, Castanea sativa, Pinus sylvestris, and Picea orientalis wood samples at 8%, 12%, and 15% moisture content (MC) were machined on a CNC router in both across and along the grain directions. Based on the experimental data of surface roughness and cutting power analyses, a total of 16 models were used. These were selected in hundreds of models that have the lowest error. The spindle speed, feed rate, and the number of cutter teeth were chosen to be different with the literature based on the length of cutter mark. As a result, optimum machining parameters were determined for each wood MC.

PENGARUH POSISI SAMBUNGAN KONSTRUKSI KAYU TERHADAP DEDAIN PRODUK MEBEL BERBAHAN DASAR KAYU

Wood furniture products were one of the commodities that have a dominant contribution compared to other furniture materials to the Indonesian economy. In furniture products, the connection system was a weak point in the construction, so a detailed analysis was needed regarding the factors that affect the strength of the construction and the effectiveness of the wood connection system. The purpose of this study was to determine the quality of the wood used as outdoor chair material by carrying out several tests to obtain wood density, moisture content, MOR and MOE values and then carrying out impact tests on actual outdoor chair products. The results showed that the teak wood used in the raw material for making the product had a moisture content of 12% with an average density of 0.68 g/cm3. The results of the static flexural strength test showed that the MOE of the tested teak was 107,108 kg/cm2 and the MOR value was 1,018 kg/cm2. The compressive strength value parallel to the fiber is 536 kg/cm2. The teak sample tested was included in strong class II which is quite strong as a raw material for furniture such as outdoor chairs. Analysis of the results of the construction design found that the type of construction used was tenon mortise, cracks at the joints occurred because the tenon was too close to the head of the wood. Based on the product test results, after the product with a new construction design was made, by lowering the tenon mortise position 3 mm from the initial position. The crack that occurs in the product is caused by an error in product construction design and not from the quality of the product raw materials used.

The Role of Drying Schedule and Conditioning in Moisture Uniformity in Wood: A Machine Learning Approach.

Monitoring the moisture content (MC) of wood and avoiding large MC variation is a crucial task as a large moisture spread after drying significantly devalues the product, especially in species with high green MC spread. Therefore, this research aims to optimize kiln-drying and provides a predictive approach to estimate and classify target timber moisture, using a gradient-boosting machine learning model. Inputs include three wood attributes (initial moisture, initial weight, and basic density) and three drying parameters (schedule, conditioning, and post-storage). Results show that initial weight has the highest correlation with the final moisture and possesses the highest relative importance in both predictive and classifier models. This model demonstrated a drop in training accuracy after removing schedule, conditioning, and post-storage from inputs, emphasizing that the drying parameters are significant in the robustness of the model. However, the regression-based model failed to satisfactorily predict the moisture after kiln-drying. In contrast, the classifying model is capable of classifying dried wood into acceptable, over-, and under-dried groups, which could apply to timber pre- and post-sorting. Overall, the gradient-boosting model successfully classified the moisture in kiln-dried western hemlock timber.

Biological Deterioration and Natural Durability of Wood in Europe

In recent years, the use of wood has gained social interest, leading to a global increase in its demand. Yet, this demand is often covered by the production of woods of low natural durability against biological deterioration. The main biological agents with the potential to attack the structural integrity of wood are wood-decay fungi, saproxylic beetles, termites, and marine molluscs and crustaceans. In most circumstances, fungi are the main wood-deteriorating agents. To attack the cell wall, wood-decay fungi combine a complex enzymatic mechanism with non-enzymatic mechanisms based on low-molecular-weight compounds. In some cases, the larvae of saproxylic beetles can also digest cell wood components, causing serious deterioration to wooden structures. The impact of subterranean termites in Europe is concentrated in the Southern countries, causing important economic losses. However, alien invasive species of voracious subterranean termites are expanding their presence in Europe. Wooden elements in permanent contact with marine water can be readily deteriorated by mollusc and crustacean borers, for which current preservatives lack efficacy. The natural durability of wood is defined as the inherent resistance of wood to catastrophic action by wood-destroying organisms. Besides exposure to the climate, product design and use conditions, the natural durability of wood is key to the prediction of the service life of wooden products, which can be shortened due to the impact of global change. The major wood properties involved in natural durability are related to the composition of lignin in the cell wall, the anatomy of the xylem, nutrient availability, the amount and composition of heartwood extractives, and the presence of moisture-regulating components since wood moisture content influences the establishment of wood-degrading organisms.

Strain measurement in glulam timber for bridges with embedded strain gauges and detection of moisture-variation effects

ABSTRACT As an ecological and renewable material with good mechanical and geometrical characteristics, glulam is becoming more and more interesting in the construction of timber bridges. However, due to their exposure to outdoor conditions, these structures are subject to climatic wetting/drying (W/D) cycles, and consequently undergo numerous dimensional variations of shrinkage/swelling, thus impacting the durability of these structures. This study first proposes an accelerated W/D cycle to simulate the moisture content (MC) variations present in timber bridges, i.e. between 10% and 30% MC. For this purpose, a climatic chamber controlled in temperature and relative humidity, and immersion tanks were used to accelerate the wood MC diffusion. Subsequently, the monitoring of strain by gauges embedded in the core of the specimen was carried out to apprehend the shrinkage/swelling mechanisms induced by the W/D cycles. The results show that the bonding pressure applied during the manufacturing of glulam does not alter the measuring capacity of the gauges, and that the strain gauges allow to quantify the behaviour of the different glulam lamellae. The measurements and microstructural observations by X-ray tomography also revealed the damage to the wood under the effect of W/D cycles.

The effect of frequency and temperature on dielectric properties of wood with high moisture content

Abstract Dielectric sensors are a popular choice for determining wood moisture content. However, the output of these devices, especially when measuring high moisture content, may be significantly affected by the moisture content itself, by sensor frequency (f) and by environmental temperature (T). This study investigated the effect mechanism of f and T on dielectric properties of wood with different moisture contents. Dielectric constant (ε) and dielectric loss factor (tan δ) for Populus nigra, Tilia tuan, Abies fabri and Fraxinus mandshurica wood samples of various moisture contents were measured from 1 to 107 Hz and from – 40 to 25 °C. The results show that wood ε increases with increasing moisture content and temperature, and decreases with increasing f. The dielectric constant depends significantly on f when T exceeds 6 °C, the rate of ε decreases with increasing f. At room temperature, tan δ of wood with moisture content >50% were not related, and peaked between 103 and 104 Hz. The change of tan δ with T is complex. The results provide a basis for in-depth research on the dielectric properties of wood with high moisture content and a theoretical basis for the measurement and calibration of the moisture content of standing trees.

Effect of ambient hygrothermal conditions on wood moisture content in the crawl spaces of wooden houses with insulated and airtight foundations as well as conventional foundations in Hokkaido and Akita

わが国の木造住宅の床下環境は構法の変遷とともに変化しており，現在は床下土壌現しよりも床下防湿コンクリート打ちが主流で，寒冷地を中心に床下換気孔を持たない基礎断熱工法も広まってきている。そこで本研究では，居住者のある住宅を対象に，至近に建つ4棟の木造住宅の床下温湿度を1年間実測する調査，新しい基礎仕様である基礎断熱の木造住宅１棟の床下等の温湿度および木材含水率を17年間の長期にわたり実測する調査の2つを行い，異なる基礎仕様が土台等の床下木材に与える影響を検討した。その結果，基礎断熱の住宅の床下環境はいずれも年間を通して相対湿度40～80％の低湿に保たれており，床下木材が高含水率となる危険性はなかった。一方，床下換気孔を持つ在来型の基礎の場合は夏季に相対湿度が80％を超える高湿度期間が確認され，床下木材が高含水率となる懸念があった。さらに床下防湿コンクリート打ちの住宅は床下土壌現しの住宅よりも高湿度の影響が大きく，これは床下が低温となることに起因することが分かった。

The effect of partial delignification on the stress–strain relationship in transverse compression

Due to very significant improvements in the mechanical performance of solid wood, densification after partial or full delignification has received renewed attention. While studies predominantly focus on isolated cases, e.g., one wood species densified in one anatomical direction, systematic investigations of the effect of wood structure on the densification process are seldom performed. The present study compares the deformation patterns of one representative softwood (spruce) and hardwood (poplar), respectively, in transverse compression. In terms of variables, the native and partially delignified state, wet and dry conditions, and three different orientations of wood grain are considered. It shows that the structural inhomogeneity of spruce wood, with low-density earlywood and high-density latewood, governs its densification pattern and hinders defect-free densification. Contrarily, diffuse-porous poplar is structurally more homogeneous, which together with more efficient softening by delignification leads to favorable densification behavior. Overall, delignification led to a significant softening of both wood species in transverse compression, which greatly enhanced the softening effect of high wood moisture content.